Introduction:

Analysis of antinuclear antibodies (ANAs) by indirect immunofluorescence (IIF) is a basic tool for the serological diagnosis of systemic rheumatic disorders. Automation of ANA IIF interpretation including pattern recognition can improve assay reproducibility and intra- and inter-laboratory variability. Automation of ANA reading meets the demand for cost-effective assessment of large numbers of samples in routine laboratories. Comparing automated and visual interpretation of ANA patterns, the usefulness for laboratory diagnostics was investigated.

Methods:

Antinuclear antibody detection by IIF on human epithelial-2 (HEp-2) cells including pattern recognition was performed in a total of 1222 consecutive sera of patients with suspected systemic rheumatic diseases from a university routine laboratory (n=924) and a private referral laboratory (n=298). IIF reading results obtained in routine diagnostics were compared with findings by a novel automated interpretation system employing mathematical pattern recognition algorithms.

Results:

Visual and automated interpretation of ANA showed a very good agreement regarding positive / negative discrimination (kappa=0.828). Only 98 (8.0%) of 1222 sera demonstrated discrepant results in the differentiation of positive from negative samples. The contingency coefficient of Chi-square statistics was 0.646 for the university laboratory cohort with an agreement of 93.0% and 0.695 for the private laboratory cohort with an agreement of 90.6%, p<0.0001, respectively. According to the McNemar test, there was no significant difference in the university cohort (1.08%, p=0.25).